Marmots, which live in the high Sierra above tree line, have already gone into hibernation in Yosemite National Park. Biologists believe they were driven into hibernation early because they sensed impending big snows. less

Marmots, which live in the high Sierra above tree line, have already gone into hibernation in Yosemite National Park. Biologists believe they were driven into hibernation early because they sensed impending big ... more

Sharks! Sharks everywhere! Great white sharks are making themselves known in numbers as warm waters entice things they like to eat. Waters off San Francisco are 7-10 degrees warmer than usual.

Sharks! Sharks everywhere! Great white sharks are making themselves known in numbers as warm waters entice things they like to eat. Waters off San Francisco are 7-10 degrees warmer than usual.

Photo: Courtesy Stanford University

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A rare sighting of a northern fur seal in San Francisco Bay was also made recently on a nature trip with the Golden Gate Audubon Society. Bill Keener of the Golden Gate Cetacean Research organization said that a live northern fur seal has never been seen by the group (dating back to the 1970s), although fur seal bones from 1300 have been found in Emeryville so the sighting was not completely without precedent. less

A rare sighting of a northern fur seal in San Francisco Bay was also made recently on a nature trip with the Golden Gate Audubon Society. Bill Keener of the Golden Gate Cetacean Research organization said that ... more

Migration patterns are changing (or at least temporarily getting funky) due to warmer waters further up the coast. The extremely rare Bryde's whale is thought to only live in the Gulf of Mexico, but a few were sighted off Dana Point in SoCal recently. less

Migration patterns are changing (or at least temporarily getting funky) due to warmer waters further up the coast. The extremely rare Bryde's whale is thought to only live in the Gulf of Mexico, but a few were ... more

to the waters off the Channel Islands. They're normally found in Mexico, but warm El Niño waters have lured them much farther north.

Photo: David McNew, Getty Images

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Ocean levels have risen: Sea-surface heights are up 50 cm across the Pacific, a phenomenon that occurs when the waters warm.

Ocean levels have risen: Sea-surface heights are up 50 cm across the Pacific, a phenomenon that occurs when the waters warm.

Photo: Earth.nullschool.net

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A stretch of the Pacific Ocean along the equator is warmer than normal, which is what happened in advance of the 1997 El Niño. Warm waters are pushing east toward the Americas as trade winds that usually push those waters toward Asia weaken.

This is a map of sea water temperatures indicating the El Niño effect.

A stretch of the Pacific Ocean along the equator is warmer than normal, which is what happened in advance of the 1997 El Niño. Warm waters are pushing east toward the Americas as trade winds that usually push

The image of the Pacific Ocean in 2015, left, and during the massive El Niño in early 1998 are very similar. The image was produced using sea surface height measurements by satellite. Sea surface height is an indicator of the heat content of the ocean. less

The image of the Pacific Ocean in 2015, left, and during the massive El Niño in early 1998 are very similar. The image was produced using sea surface height measurements by satellite. Sea surface height is ... more

It's not just humans enjoying the fish. Marine critters are feasting on an influx of anchovies that have been chased to coastal waters by rising water temps.

It's not just humans enjoying the fish. Marine critters are feasting on an influx of anchovies that have been chased to coastal waters by rising water temps.

Photo: Jim Wilson, New York Times

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A group of tourists got to witness the savagery of nature up close and personal when a great white shark munched on a seal just a few feet off a dock on Alcatraz Island.

A group of tourists got to witness the savagery of nature up close and personal when a great white shark munched on a seal just a few feet off a dock on Alcatraz Island.

Photo: YouTube

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Huge schools of bluefin tuna like this one arrived in Monterey Bay recently.

Huge schools of bluefin tuna like this one arrived in Monterey Bay recently.

Photo: Randy Wilder, Monterey Bay Aquarium

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If you've been whale-watching lately, it's been quite a season. Here's a humpback whale in full breach near the Southeast Farallon Island — researchers stationed at the island counted 93 humpback whales, 21 blue whales and one fin whale in a single hour. Whales are moving to where the food is — increasingly in waters closer to shore. In Oregon, whales have even been seen in the Columbia River. less

If you've been whale-watching lately, it's been quite a season. Here's a humpback whale in full breach near the Southeast Farallon Island — researchers stationed at the island counted 93 humpback whales, 21 ... more

Photo: Peter Winch/Oceanic Society

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White pelicans, which can range to a 9-foot wingspan and weigh 25 pounds, are rare on the Pacific Coast, but up to 300 per trip have been sighted in Elkhorn Slough.

White pelicans, which can range to a 9-foot wingspan and weigh 25 pounds, are rare on the Pacific Coast, but up to 300 per trip have been sighted in Elkhorn Slough.

And some of that hurricane moisture ended up north in the Sierras, where July rainfall was 200-800 percent of normal levels. So if you expected blue summer skies at Tahoe and got thunderstorms instead, now you know why. less

And some of that hurricane moisture ended up north in the Sierras, where July rainfall was 200-800 percent of normal levels. So if you expected blue summer skies at Tahoe and got thunderstorms instead, now you ... more

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After an already wet week, the Bay Area is expected to get yet another round of rainfall on Friday evening, forecasters said.

This round of precipitation, however, is expected to be lighter than that what fell earlier this week, according to forecasters. Showers are predicted to move in by 8 p.m. before the bulk of the rainfall comes between 2 and 4 a.m. on Saturday, leaving behind around a quarter of an inch of precipitation across the region, said Drew Peterson, a forecaster with the National Weather Service in Monterey.

Compared to the El Niño-charged rain storms that hit the Bay Area on Sunday through Wednesday, this round is “not nearly as impressive,” he said.

The rain should linger until late Saturday morning before the weather turns dry again Sunday. Yet another rain system is possible Monday before a more robust storm is predicted to move in on Wednesday, Peterson said.